OmegaMan's Musings

Not finding a satisfactory method to find invalid Azure Container names, I wrote my own easier (?) to read regex pattern for .Net.

^                       # Anchor; beginning of line. 
(?!.+--)                # String ahead does not contain two dashes 
(?!^-)                  # String ahead does not start with a dash 
(\$root|[a-z\d-]{3,63}) # Either literal root or a combination of lower case. 
$                       # Anchor; end of line

Using a negative look ahead convention (which does not match anything) to handle the double dash situation makes it easier to read.

The first rule says from the beginning of the line, there should not be two dashes or to start with a dash. Once valid, then either match the literal text “$root” or then match only lower case letters, numbers or a dash for a total of three characters to 63 characters.

Remember to run the above pattern with IgnorePatternWhiteSpace, which allows us to comment it. Or run without any option by specifying it on one line:

^(?!.+--)(?!^-)(\$root|[a-z\d-]{3,63})$

Here are the rules for Container names:

Valid naming for a Container in Azure Blob Storage.

1.  3 to 63 Characters

2.  Starts With Letter or Number

3.  Letters, Numbers, and Dash (-)

4.  Every Dash (-) Must Be Immediately Preceded and Followed by a Letter or Number

5.  All letters in a container name must be lowercase.